This invention relates generally to an extremum seeking, closed-loop control system for maximizing the power of a power producing machine, and more specifically to an electronic implementation of such a control system.
There is disclosed in U.S. Pat. No. 3,142,967 to Paul H. Schweitzer a method and apparatus for optimizing the power output of a machine by introducing periodic perturbations (hereinafter referred to as dithering) of a control parameter and monitoring the effect of the dithering on the torque or speed of the machine. If the machine regularly accelerates while the parameter is on the increase, the control system will cause an increase in the parameter setting. If the machine regularly decelerates while the parameter is on the increase, the control system will cause a decrease in the parameter setting. Where machine acceleration results from a momentary downward adjustment of the parameter, the control system operates to decrease the parameter setting. However, where a momentary decrease in the parameter setting causes the machine to decelerate, the control system adjusts the parameter setting upward.
The implementation described in the aforereferenced Schweitzer patent is mechanical in nature and, as such, is somewhat difficult to adapt to a wide range of machines. For example, when applying the invention to the internal combustion engine of an automobile, problems arise due to the wide variations among manufacturers in the location and construction of the engine speed controlling parameters and the space availability for properly mounting the optimizer structure. As a result, the invention has not met with wide reception as an add-on feature due to the installation problem and the higher cost resulting from the necessity of customizing the unit.
The present invention obviates these problems. Rather than a mechanical implementation, the optimizer control of the present invention employs solid-state electronic digital type circuitry which is comparatively inexpensive to manufacture, universal in application and simple to install in a wide variety of applications.
More specifically, in accordance with the teachings of the present invention, an electronic oscillator is provided for producing dither pulses of a relatively long duration and low repetition rate. The dither pulses are applied to a suitable transducer such as an electric motor or solenoid which is used to produce slight variations of a speed controlling parameter of the engine. Coupled to the engine shaft is an electrical pulse generating device which produces pulses of a relatively high rate compared to the rate at which the dither pulses are produced by the oscillator. Also, the high frequency pulses are produced at a rate which is directly proportional to the speed of the engine's output shaft.
The dither pulses are also applied to timing networks which effectively divide the dither pulse period into segments. The output of the timing networks are coupled through coincidence circuits (AND gates) to the input terminals of an up-down pulse counting network. Applied to second inputs of these AND gates are the high frequency pulses whose rate is proportional to the instantaneous angular velocity of the output shaft. Thus, during a first portion of a dither pulse, the counter network counts up the number of high frequency pulses received and subsequently, during a second equal portion of the dither pulse, the counter network is decremented by the number of high frequency pulses received during this second time interval. If the count passes through zero, it is known that the engine shaft has accelerated as a result of the dithering of the speed controlling parameter. However, if the count remains positive during the countdown period, it is known that the engine shaft has decelerated. Thus, the counter serves to develop the algebraic difference (difference with sign) of the engine shaft speed indicating pulses occurring during successive intervals of a dither pulse.
The output from the counter is coupled through a logic device including flip-flops and gates, to a suitable transducer whose output is used to either increase or decrease the parameter setting so as to maximize the engine shaft speed and torque.